Feeding our gut bacteria meat may enhance heart disease risks

Antibiotics or vegetarian diets block production of a risk-associated chemical.

Americans eat much more red meat than most other people, and Americans get a lot more cardiovascular disease than most other people. Red meat has lots of saturated fats and cholesterol, which causes cardiovascular disease, right? Not so fast. As with many commonly held assertions, especially in the field of nutrition, this one sounds good but does not quite have the data to support it.

Intestinal microbiota, or gut flora, are a trendy health topic right now; their importance has only been acknowledged in the past twenty years or so, but they have already been shown to impact such vital physiological processes as immune function and the development of cancer, diabetes, and obesity. Dietary choices—like the choice to eat red meat or not—are known to influence the relative ratios of the different bacterial species residing in our guts.

So researchers at the Cleveland Clinic decided to check out how different intestinal microbiota metabolize the components of meat. They found that bacteria present in the intestines of omnivores, but not present in the intestines of vegans or vegetarians, generate a molecule that promotes atherosclerosis when they are fed red meat.

L-carnitine is a compound found in meat, hence the name carnitine. (Does it make you crave carne asada too?) Eukaryotes can produce it, but only prokaryotes can break it down. When fed L-carnitine, either in pills or in a steak (or both), omnivores metabolize it to generate the breakdown product trimethylamine –N-oxide (TMAO); vegans and vegetarians don’t.

But if the omnivores have been given broad spectrum antibiotics that kill the bugs in their guts, they don’t either. This suggests that TMAO is a product of these gut bacteria.

(Please note that no vegans were harmed in the course of this experiment, although one guy did decide to have an eight-ounce sirloin in the name of science after over five years of abstinence.)

In a cohort of 2,595 people undergoing elective cardiac evaluation, fasting plasma L-carnitine levels were associated with an increased risk of cardiovascular disease and its nefarious effects—heart attack, stroke, and death—in a dose-dependent manner. But this association only held true in people who also had high levels of TMAO. TMAO promotes atherosclerosis, but the mechanism by which it does so is not entirely clear. It seems to work at least partially by inhibiting reverse cholesterol transport—the transport of cholesterol from the peripheral tissues back to the liver.

L-carnitine is essential for transporting fatty acids into mitochondria. It has been given as an oral supplement to people on hemodialysis and as treatment for heart trouble, of all things. The authors of this paper suggest that, given their results, such supplementation might not be the best idea.

Short story: the study's headline is a bit misleading, as other foods appear to have a much greater effect on TMAO levels than red meat (including seafood, which is supposed to be protective of your heart!).

This headline and the accompanying article are very poorly written. I'm not one to generally complain about these types of things, but I'm making an exception in this case ;-)

First, the headline: "enhance" is absolutely the wrong word here. How do you "enhance" risks? I want to know if they make the risks higher, or lower. I would suggest "increase" or "decrease." If you "enhance risk" are you increasing the risk (given the risk is bad), or are you decreasing it (given enhance is aligned with "good" in most cases).

Second, after not being clear on whether risk is increased or decreased, the supporting story isn't clear. I read it twice and the subject flip flops so many times I still can't tell if the risk is increased or decreased.

Please, make an edit and clarify for this. Ars does have editors, right?

After only reading the article headline, I came to the conclusion that getting a meat enema can be a cause of cancer. Then I just had to read the article. Can this gut flora mutation be attributed to red meat being usually fed antibiotics?

Seriously, the human body can get all the nutrients it requires from a vegan/vegetarian diet. I personally think that the average "western" diet is way more unbalanced and unhealthy than the diet of people who do not eat meat or animal products (I think the epidemiological trends prove that - don't see many obese vegetarians/vegans with diabetes...). Granted: The vegan diet can push it a bit by excluding dairy, but most people who actually care enough to think about what kind of foods they choose are pretty health conscious and aware of the limits.

Short story: the study's headline is a bit misleading, as other foods appear to have a much greater effect on TMAO levels than red meat (including seafood, which is supposed to be protective of your heart!).

In addition -- though this is not related to headlines -- given the study's own conclusions, it would seem far more appropriate to kill off TMAO-generating bacteria than it would to reduce either red meat or seafood intake, given that otherwise these foods have well-known benefits.

Seriously, the human body can get all the nutrients it requires from a vegan/vegetarian diet. I personally think that the average "western" diet is way more unbalanced and unhealthy than the diet of people who do not eat meat or animal products (I think the epidemiological trends prove that - don't see many obese vegetarians/vegans with diabetes...). Granted: The vegan diet can push it a bit by excluding dairy, but most people who actually care enough to think about what kind of foods they choose are pretty health conscious and aware of the limits.

Corrected that for you. While vegetarian diets can be extremely healthy as long as you don't do that classic thing of substituting cheese into every dish. Vegan diets really do fail at being balanced, ignoring the showstopper of B12, they have reduced levels of many other nutrients such as EPA. It is incredibly hard to balance a vegan diet, even harder if you try to do the environmentally aware thing of trying to eat locally sourced in season (non-greenhouse grown) food. This is especially ironic given many "ethical" vegans will preach about how their diet uses less global resource amongst other propaganda.

Also you do see obese vegetarians, quite a lot in fact since dairy and high fat nuts often fulfil the role of meat in their meals (often very nice they are too - but you can sick nut roast up where the sun don't shine; it's like baked gravel). Many choose to be vegetarians for reasons other than health (e.g. dislike meat, religion, ethical values) and like so many meat eaters many of those don't look out for their health and end up overweight. Of course the stats are sewed by the heath fanatics amongst their numbers.

More telling than difficult to control epidemiological food studies is the fact that no human civilisation has ever been recorded to subsist purely on a vegan diet (the last candidate was dismissed when they found they opportunistically supplemented their diet with insects).

Short story: the study's headline is a bit misleading, as other foods appear to have a much greater effect on TMAO levels than red meat (including seafood, which is supposed to be protective of your heart!).

So the author is likely a vegetarian and let their anti-meat bias screw up their article?

Short story: the study's headline is a bit misleading, as other foods appear to have a much greater effect on TMAO levels than red meat (including seafood, which is supposed to be protective of your heart!).

What's more, according to the analysis that you cited, peanuts, mushrooms, potatos and peas have a greater effect on Carnitine levels than beef (at least as compared to the control group that the authors used).

This story is just sensationalism (since there was little meaningful analysis). The headline could have read "feeding our gut bacteria pea may enhance haert disease risks", and would have been "more accurate".

Short story: the study's headline is a bit misleading, as other foods appear to have a much greater effect on TMAO levels than red meat (including seafood, which is supposed to be protective of your heart!).

I came here to say something similar. This is just another in a long line of poorly done studies with weakly supported conclusions that the media blows out of proportion. One important reason this study is bunk is that the authors are assuming that TMAO is definitively linked with atherosclerosis, when the evidence for that itself is weak at best, and yet the entire conclusion of their paper is dependent on that 'fact.'

They also state as 'fact' that cholesterol and saturated fat cause heart disease, which is unequivocally false. Research from the past 10-15 years has shown that some saturated fats do indeed raise total LDL (and the others are neutral), but they actually increase the proportion of large, fluffy LDL particles which have been shown to be neutral with regard to causing atherosclerosis; it's refined carbohydrates that raise the proportion of small LDL particles, which are very strongly correlated with atherosclerosis risk. Indeed, saturated fats can actually raise HDL and lower triglycerides concentrations, which are better measures of heart health than total LDL, specifically because of the somewhat recent revelation that LDL particles come in different sizes. I'm not making this up: it's all verifiable in the literature and better supported than the overly simplified concept of 'eating saturated fat raises LDL and high LDL levels cause heart disease.'

So I'm immediately skeptical of any research that purports that (heavily flawed) hypothesis as 'fact,' as they are just 'towing the party line,' so to speak.

Short story: the study's headline is a bit misleading, as other foods appear to have a much greater effect on TMAO levels than red meat (including seafood, which is supposed to be protective of your heart!).

So the author is likely a vegetarian and let their anti-meat bias screw up their article?

You may (or may not) be surprised at how often the authors of studies like this are vegetarian or vegan. They apparently have no shame.

Seriously, the human body can get all the nutrients it requires from a vegan/vegetarian diet. I personally think that the average "western" diet is way more unbalanced and unhealthy than the diet of people who do not eat meat or animal products (I think the epidemiological trends prove that - don't see many obese vegetarians/vegans with diabetes...). Granted: The vegan diet can push it a bit by excluding dairy, but most people who actually care enough to think about what kind of foods they choose are pretty health conscious and aware of the limits.

Corrected that for you. While vegetarian diets can be extremely healthy as long as you don't do that classic thing of substituting cheese into every dish. Vegan diets really do fail at being balanced, ignoring the showstopper of B12, they have reduced levels of many other nutrients such as EPA. It is incredibly hard to balance a vegan diet, even harder if you try to do the environmentally aware thing of trying to eat locally sourced in season (non-greenhouse grown) food. This is especially ironic given many "ethical" vegans will preach about how their diet uses less global resource amongst other propaganda.

Came here to post this. Humans being Omnivorous doesn't mean that we can choose one or the other, it means that we need both. Moderation, though, especially in red meat, is key: you can probably get all the benefit you need from meat by eating chicken once a week, with red meat every once in a while as a substitute.

Honestly, Americans have diet related health problems because of large portions of calorie dense, nutritionally imbalanced food. the effects of that dwarf everything else.

I find it funny how most nutrition related studies appoint an inverse proportion of deliciousness to being healthy. The more delicious the food, the bigger the chances of it being unhealthy.

As a general rule it is true. I have a vegetarian friend who swore up and down that I'd love this 100% vegetarian dish she found. Said ti was flavorful and filling. so I tried it. It was just above bland in flavor and nowhere near filling. I think people who opt for a vegetarian diet lie to themselves about how good the food tastes in order to keep with it. I'm an omnivore. I eat a little of everything and I'm in perfect health.

Short story: the study's headline is a bit misleading, as other foods appear to have a much greater effect on TMAO levels than red meat (including seafood, which is supposed to be protective of your heart!).

So the author is likely a vegetarian and let their anti-meat bias screw up their article?

You may (or may not) be surprised at how often the authors of studies like this are vegetarian or vegan. They apparently have no shame.

I'm talking about the author of this article though not the study. Scientists in general don't let their personal biases taint their work. While it does happen it's not very common. Journalists on the other had these days do allow their personal biases spin their articles away from the facts they are supposed to be presenting to us their readers.

Seriously, the human body can get all the nutrients it requires from a vegan/vegetarian diet. I personally think that the average "western" diet is way more unbalanced and unhealthy than the diet of people who do not eat meat or animal products (I think the epidemiological trends prove that - don't see many obese vegetarians/vegans with diabetes...). Granted: The vegan diet can push it a bit by excluding dairy, but most people who actually care enough to think about what kind of foods they choose are pretty health conscious and aware of the limits.

Corrected that for you. While vegetarian diets can be extremely healthy as long as you don't do that classic thing of substituting cheese into every dish. Vegan diets really do fail at being balanced, ignoring the showstopper of B12, they have reduced levels of many other nutrients such as EPA. It is incredibly hard to balance a vegan diet, even harder if you try to do the environmentally aware thing of trying to eat locally sourced in season (non-greenhouse grown) food. This is especially ironic given many "ethical" vegans will preach about how their diet uses less global resource amongst other propaganda.

Came here to post this. Humans being Omnivorous doesn't mean that we can choose one or the other, it means that we need both. Moderation, though, especially in red meat, is key: you can probably get all the benefit you need from meat by eating chicken once a week, with red meat every once in a while as a substitute.

Honestly, Americans have diet related health problems because of large portions of calorie dense, nutritionally imbalanced food. the effects of that dwarf everything else.

Americans also aren't active enough in general which adds to the problems from their poor dietary choices. Many eat like farmers but lead the lives of a sloth.

I find it funny how most nutrition related studies appoint an inverse proportion of deliciousness to being healthy. The more delicious the food, the bigger the chances of it being unhealthy.

As a general rule it is true. I have a vegetarian friend who swore up and down that I'd love this 100% vegetarian dish she found. Said ti was flavorful and filling. so I tried it. It was just above bland in flavor and nowhere near filling. I think people who opt for a vegetarian diet lie to themselves about how good the food tastes in order to keep with it. I'm an omnivore. I eat a little of everything and I'm in perfect health.

Nah, she just has crap taste or is a bad cook. Almost all seasonings are plant-based, as are (obviously) delicious, delicious chili peppers. It may be a bit harder, but you can make delicious flavorful and entirely vegetarian meals. I'm not vegetarian (and hate vegans), not that my preferences are in any way relevant, but I've eaten them.

Honestly, Americans have diet related health problems because of large portions of calorie dense, nutritionally imbalanced food. the effects of that dwarf everything else.

I'm a Canadian living in the U.S. married to an American, when I was dating my wife my mother in-law thought I didn't like her cooking because I only ate small portions -- "no thank you portions" as she called them. When I tried to explain how much smaller portions were in Canada she didn't really understand -- "How can you be full? You hardly ate anything."

I find it funny how most nutrition related studies appoint an inverse proportion of deliciousness to being healthy. The more delicious the food, the bigger the chances of it being unhealthy.

As a general rule it is true. I have a vegetarian friend who swore up and down that I'd love this 100% vegetarian dish she found. Said ti was flavorful and filling. so I tried it. It was just above bland in flavor and nowhere near filling. I think people who opt for a vegetarian diet lie to themselves about how good the food tastes in order to keep with it. I'm an omnivore. I eat a little of everything and I'm in perfect health.

Speaking from having experienced it recently(lost 70 lbs, by changing my diet:) change in diet can cause a huge change in perceived flavor. things that I used to decry as bland now taste good, some things I used to love to eat are now too rich, and not appealing.

Add that to the fact that most people overcook veggies, and that may have been what you experienced.

Seriously, the human body can get all the nutrients it requires from a vegan/vegetarian diet. I personally think that the average "western" diet is way more unbalanced and unhealthy than the diet of people who do not eat meat or animal products (I think the epidemiological trends prove that - don't see many obese vegetarians/vegans with diabetes...). Granted: The vegan diet can push it a bit by excluding dairy, but most people who actually care enough to think about what kind of foods they choose are pretty health conscious and aware of the limits.

Corrected that for you. While vegetarian diets can be extremely healthy as long as you don't do that classic thing of substituting cheese into every dish. Vegan diets really do fail at being balanced, ignoring the showstopper of B12, they have reduced levels of many other nutrients such as EPA. It is incredibly hard to balance a vegan diet, even harder if you try to do the environmentally aware thing of trying to eat locally sourced in season (non-greenhouse grown) food. This is especially ironic given many "ethical" vegans will preach about how their diet uses less global resource amongst other propaganda.

Came here to post this. Humans being Omnivorous doesn't mean that we can choose one or the other, it means that we need both. Moderation, though, especially in red meat, is key: you can probably get all the benefit you need from meat by eating chicken once a week, with red meat every once in a while as a substitute.

Honestly, Americans have diet related health problems because of large portions of calorie dense, nutritionally imbalanced food. the effects of that dwarf everything else.

Americans also aren't active enough in general which adds to the problems from their poor dietary choices. Many eat like farmers but lead the lives of a sloth.

Not as much as you might think, at least for some people: during most of my recent 70 lbs of weight loss, i was essentially idle due to a shoulder injury. and I still lost 10lbs a month, like clockwork.

Honestly, Americans have diet related health problems because of large portions of calorie dense, nutritionally imbalanced food. the effects of that dwarf everything else.

I'm a Canadian living in the U.S. married to an American, when I was dating my wife my mother in-law thought I didn't like her cooking because I only ate small portions -- "no thank you portions" as she called them. When I tried to explain how much smaller portions were in Canada she didn't really understand -- "How can you be full? You hardly ate anything."

Your story of "smaller Canadian portions" is in direct contradiction of the video evidence documented in the series "Epic Meal Time".

I find it funny how most nutrition related studies appoint an inverse proportion of deliciousness to being healthy. The more delicious the food, the bigger the chances of it being unhealthy.

As a general rule it is true. I have a vegetarian friend who swore up and down that I'd love this 100% vegetarian dish she found. Said ti was flavorful and filling. so I tried it. It was just above bland in flavor and nowhere near filling. I think people who opt for a vegetarian diet lie to themselves about how good the food tastes in order to keep with it. I'm an omnivore. I eat a little of everything and I'm in perfect health.

Speaking from having experienced it recently(lost 70 lbs, by changing my diet:) change in diet can cause a huge change in perceived flavor. things that I used to decry as bland now taste good, some things I used to love to eat are now too rich, and not appealing.

Add that to the fact that most people overcook veggies, and that may have been what you experienced.

Weight loss and having general good health are not about a simple diet change. If you aren't happy with your physical condition you don't need to look very far to find the reason. It's the lifestyle you have been living. REAL weight loss that stays off requires a change in your diet AND a change in the level of your daily physical activity. It requires a lifestyle change. Going vegetarian just to lose weight is silly. all you really need to do is eat a well balanced diet. that means eating as your body was designed to. A little bit of everything. Add to that some daily physical activity and you are golden. Our bodies were not designed for the mostly sedentary lives the modern age has many of us in the west living.

Speaking from having experienced it recently(lost 70 lbs, by changing my diet:) change in diet can cause a huge change in perceived flavor. things that I used to decry as bland now taste good, some things I used to love to eat are now too rich, and not appealing.

Add that to the fact that most people overcook veggies, and that may have been what you experienced.

Exactly, the problem isn't red meat, its far, far too much red meat (especially smoked/charred or processed e.g. saltpetre treated ham). I will be first to admit I eat to much, but I still probably eat far less than most meat eaters in the west. Meat really shouldn't be more than about 20-25% of your plate and odd vegetarian meal isn't a bad idea either.

I find it funny how most nutrition related studies appoint an inverse proportion of deliciousness to being healthy. The more delicious the food, the bigger the chances of it being unhealthy.

As a general rule it is true. I have a vegetarian friend who swore up and down that I'd love this 100% vegetarian dish she found. Said ti was flavorful and filling. so I tried it. It was just above bland in flavor and nowhere near filling. I think people who opt for a vegetarian diet lie to themselves about how good the food tastes in order to keep with it. I'm an omnivore. I eat a little of everything and I'm in perfect health.

Speaking from having experienced it recently(lost 70 lbs, by changing my diet:) change in diet can cause a huge change in perceived flavor. things that I used to decry as bland now taste good, some things I used to love to eat are now too rich, and not appealing.

Add that to the fact that most people overcook veggies, and that may have been what you experienced.

Weight loss is and having general good health not about a simple diet change. If you aren't happy with your physical condition you don't need to look very far to find the reason. It's the lifestyle you have been living. REAL weight loss that stays off requires a change in your diet AND a change in the level of your daily physical activity. It requires a lifestyle change. Going vegetarian just to lose weight is silly. all you really need to do is eat a well balanced diet. that means eating as your body was designed to. A little bit of everything. Add to that some daily physical activity and you are golden. Our bodies were not designed for the mostly sedentary lives the modern age has many of us in the west living.

Just to be clear, i didn't go vegan or vegetarian. I reduced portion size and decreased time between meals: 200 kcal every 2 hrs, totaling out to about 1200 to 1400 kcal a day. One side effect of eating 200 kcal meals, however, is that if you want to feel satisfied by your meals, you end up including less calorie dense foods, which generally means more veggies.

Eating veggie or vegan in the US is hard: either there isn't anything on the menu, or the things that are, are designed for people want to eat as bland as possible to feed into their superiority complex about being veggie/vegan.

There are multiple issues with this study. Not the least of which is that they commit the same fallacy as the original linking of protein to kidney disease that was a major cause of the food guide to be the way it is and ultimately the American population to be massively overweight:

That is they don't demonstrate that the chemical actually causes heart disease in any normally functioning system, only mice, and only mice with a genetic defect that prevents them from processing cholesterol properly. (The original study that said that protein causes kidney disease and ultimately failure was done on people that already had damaged kidneys!)

In fact, the every chemical produced in this study has previously been linked to high carb diets and given that they didn't control for carb intake in the study, this becomes a joke.

So once again this is a "the sky is falling on red meat" conclusion with absolutely no evidence thereof.

When they have a study of 1000 people over 10 years and have controlled for things like smoking (the only previous long term study that linked red meat to cardiovascular disease didn't control for smoking!!! to say nothing of the cherry picking of data surrounding saturated fat that resulted in the author to be put in jail in the UK.) etc. etc. etc. then get back to me. Until then there is still absolutely 0 credible evidence that red meat, which humans have been eating since before we came out of the trees and thus we are highly adapted to eat causes any harmful side effects in normal healthy humans.

Thus there is absolutely no story here folks, other than media piling on the heat for red meat that goes back to the 1970s care of the government concocting ways to get people to eat less meat thus enabling the food supply to actually feed everyone and to keep people in power, because as governments everywhere will tell you, (see Tunisia and Egypt with $600 US loafs of bread before they revolted) the fastest way to be thrown out of power is to have a hungry populous.

Short story: the study's headline is a bit misleading, as other foods appear to have a much greater effect on TMAO levels than red meat (including seafood, which is supposed to be protective of your heart!).

I came here to say something similar. This is just another in a long line of poorly done studies with weakly supported conclusions that the media blows out of proportion. One important reason this study is bunk is that the authors are assuming that TMAO is definitively linked with atherosclerosis, when the evidence for that itself is weak at best, and yet the entire conclusion of their paper is dependent on that 'fact.'

They also state as 'fact' that cholesterol and saturated fat cause heart disease, which is unequivocally false. Research from the past 10-15 years has shown that some saturated fats do indeed raise total LDL (and the others are neutral), but they actually increase the proportion of large, fluffy LDL particles which have been shown to be neutral with regard to causing atherosclerosis; it's refined carbohydrates that raise the proportion of small LDL particles, which are very strongly correlated with atherosclerosis risk. Indeed, saturated fats can actually raise HDL and lower triglycerides concentrations, which are better measures of heart health than total LDL, specifically because of the somewhat recent revelation that LDL particles come in different sizes. I'm not making this up: it's all verifiable in the literature and better supported than the overly simplified concept of 'eating saturated fat raises LDL and high LDL levels cause heart disease.'

So I'm immediately skeptical of any research that purports that (heavily flawed) hypothesis as 'fact,' as they are just 'towing the party line,' so to speak.

Or course it's far more complex even than that, in that it is largely influenced by genetics, good advise for one individual could be very bad for another (classic example those that suffer from hypercholesterolemia absolutely must avoid cholesterol and saturated fat) due to natural variation in lipid and carbohydrate metabolism. It is why the literature is so confused and apparently contradictory especially since many studies have been performed on sufferers of hypercholesterolemia or equivalent animal models. However, I would apply caution to taking the statement "large, fluffy LDL particles which have been shown to be neutral with regard to causing atherosclerosis" at face value simply because LDL v HDL levels have such good prognostic value in the clinic.

My take from every new "discovery" on what causes health problems is if you eat it, it's bad for you. Seriously. Look at every diet that's proposed. You will find some counter-evidence stating that it will cause a health issue either from the food itself or a lack of something in the diet.

Not saying eat meat, ignore veggires or vice versa but virtually everything we consume has some negative nasty to it. What are we left with? I try (and at times fail) to eat a good, balanced diet of everything but no matter what I consume, someone is going to find it causes something bad. Usually cancer.